He said his phone was "blowing up" with messages but he didn't want to be rude and answer the messages while sitting in the audience, so he ignored them until a woman from Disney poked him on the shoulder. She told him to shut off his phone because it was on. He didn't believe her until he looked.

"I thought I was going to get fired," he said.

Ruffalo spoke with Stephen Colbert on "The Late Show" in November and said he just didn't shut off his Instagram feed when entering the movie because he didn't know how the app worked.

"In my defense, [Marvel/Disney] asked me to do an Instagram live post," he said. "So I pushed the button, which you think is going to stop it, but then there's another button to stop it. ... So I ended up shoving it in my pocket and sitting down and watching the movie."

At least Ruffalo isn't the only cast member to have trouble keeping secrets. Tom Holland, who plays Spider-Man, has been named the "least trustworthy" by some of his fellow "Infinity War" cast members for his previous slips with spoilers.

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